1. Technical Field
The present invention relates to a multilayer ceramic coil and a compact motor (hereafter referred to motor) using the same.
2. Background Art
As shown in FIG. 4, a typical conventional brushless motor comprises
a plurality of coils 34 fixed on printed board 36 by soldering, and magnet 35 fixed on rotor frame 32 and opposing coils 34 across a gap.
A brushless motor of the above configuration has been provided with coils wound by metal wire. Nowadays, however, along with recent advances in printed wired board technology, a different coil manufacturing method is disclosed, e.g., in the Japanese publication of patent application No. S57-68565, No. S57-186940, No. S57-68656 or No. S58-33958. In this method, a printed pattern of a conductive coil pattern is applied on film 40 composed of epoxy resin, polyester resin and polyimide resin or the like to form coil sheet 44, and laminate a lot of those coil sheets 44 to form a multilayer coil, as shown in FIG. 5.
Such multilayer coil is advantageous to make a compact motor because a conventional core wound by metal wire is not necessary and wire winding density is high.
But the conventional multilayer coil mentioned above needs an additional process to apply an adhesive layer evenly on a plurality of respective coil sheets 44 for bonding, which results in the problem of high production costs.
Additionally, the coil sheet composed of plastic or composite materials has a poor thermal resistance and is easily affected by ambient temperature. Therefore, operation conditions such as the ambient temperature for a brushless motor must be restricted to prevent an unstable movement caused by heat generation due to copper loss and iron loss.
Consequently, in order to solve the above problems of the conventional multilayer coils, a method of manufacturing a coil configuration is disclosed in the Japanese publication of patent application No. H5-336712 which, as shown in FIG. 6, includes:
(a) forming a conductive coil pattern on a glass substrate,
(b) providing the conductive coil pattern with a glass coating, and
(c) forming a conductive coil pattern further on the glass coating, and
finally, applying a glass coating on the top surface to produce a multilayer coil.
Generally, however, the glass used for such multilayer substrate has drawbacks of low impact resistance and a short performance life.